grep/file masks - Revision history

Woozle at 15:13, 21 June 2022

2022-06-21T15:13:28Z

← Older revision		Revision as of 15:13, 21 June 2022
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	'''Example''': {{fmt/code\|grep -r [text_to_find] *.log}} will not (in most contexts, including those where it's most likely to be used e.g. searching inside {{fmt/code\|/var/log}}, because it will skip folders that don't ''also'' match the filemask -- i.e. it will only search in folders that end in {{fmt/code\|.log}}.		'''Example''': {{fmt/code\|grep -r [text_to_find] *.log}} will not (in most contexts, including those where it's most likely to be used e.g. searching inside {{fmt/code\|/var/log}}, because it will skip folders that don't ''also'' match the filemask -- i.e. it will only search in folders that end in {{fmt/code\|.log}}.

	'''Example''': If the file-mask finds too many matches in the current folder, it can generate the error {{fmt/quote\|bash: /bin/grep: Argument list too long}} -- even if the number of files ''with matching contents'' is zero or quite short.		'''Example''': If the file-mask finds too many matches in the current folder, it can generate the error {{fmt/quote\|bash: /bin/grep: Argument list too long}} -- even if the number of files ''with matching contents'' is zero or quite short. (In one case where I ran into this problem, the directory contained 5014 files.)

	In short, grep does not have the ability to search recursively using a file-mask, and any mask entered:		In short, grep does not have the ability to search recursively using a file-mask, and any mask entered:

Woozle at 15:11, 21 June 2022

2022-06-21T15:11:33Z

← Older revision		Revision as of 15:11, 21 June 2022
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	==About==		==About==
	~~[[grep]] does not effectively support recursive searching with anything but a wide-open~~ file ~~mask~~ (~~""). In other words,~~ e.g. {{fmt/code\|~~grep -r [text_to_find]~~ .log}} ~~will not (in most contexts, including those where it's most likely to be used e.g. searching inside~~ {{fmt/code\|~~/var/log~~}}, ~~because~~ it ~~will skip folders that don~~'t ''~~also~~'' ~~match the filemask~~ -- ~~i.e. it will only search in folders~~ that ~~end in {{fmt/code\|.log}}~~.		If ''file'' is specified using wildcards (e.g. {{fmt/code\|.log}} or {{fmt/code\|}}), [[bash]] (the default command-line parser) [[bash/globbing\|expands this into a listing of all matching files]] before passing it to grep. This interferes with [[grep]]'s ability to search multiple files. It can be overridden with quotes or escapes, but grep does not seem to have any wildcard-processing ability of its own (though grep ''must'' do some when it's doing recursion; to be investigated) -- so any wildcards passed through ''without'' expansion are seen by grep as names of files that don't exist.

	~~This is because~~ grep ~~does not do its own file~~-~~filtering but relies entirely on the [~~[~~command line~~]~~] environment~~ to ~~translate~~ file-mask ~~specifications into a list of files~~, ~~which are then each passed to grep as a separate argument. [[~~bash/~~globbing\|This is a feature~~/~~defect~~ of ~~<code>bash</code>]] and possibly most other Linux [[command shell]]s (investigation needed)~~.		'''Example''': {{fmt/code\|grep -r [text_to_find] *.log}} will not (in most contexts, including those where it's most likely to be used e.g. searching inside {{fmt/code\|/var/log}}, because it will skip folders that don't ''also'' match the filemask -- i.e. it will only search in folders that end in {{fmt/code\|.log}}.

			'''Example''': If the file-mask finds too many matches in the current folder, it can generate the error {{fmt/quote\|bash: /bin/grep: Argument list too long}} -- even if the number of files ''with matching contents'' is zero or quite short.

	In short, grep does not have the ability to search recursively using a file-mask, and any mask entered:		In short, grep does not have the ability to search recursively using a file-mask, and any mask entered:
	* will apply only to the current folder		* will prevent grep from recursively searching any folders whose names do not also match (so, typically will only apply to the current/top folder)
	* will prevent grep from recursively searching any folders whose names do not also match		* may prevent grep from being able to work at all if too many files in the top folder have names that match the wildcard pattern

			See [[bash/globbing]] for more discussion.
	==Links==		==Links==
	* '''2020-02-04''' [https://toot.cat/@woozle/103602468124365262 #softwareGripe #grep #counterintuitive]		* '''2020-02-04''' [https://toot.cat/@woozle/103602468124365262 #softwareGripe #grep #counterintuitive]

Woozle at 17:58, 19 June 2022

2022-06-19T17:58:31Z

← Older revision		Revision as of 17:58, 19 June 2022
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			==About==
			[[grep]] does not effectively support recursive searching with anything but a wide-open file mask (""). In other words, e.g. {{fmt/code\|grep -r [text_to_find] .log}} will not (in most contexts, including those where it's most likely to be used e.g. searching inside {{fmt/code\|/var/log}}, because it will skip folders that don't ''also'' match the filemask -- i.e. it will only search in folders that end in {{fmt/code\|.log}}.

	This is because grep does not do its own file-filtering but relies entirely on the [[command line]] environment to translate file-mask specifications into a list of files, which are then each passed to grep as a separate argument. [[bash/globbing\|This is a feature/defect of <code>bash</code>]] and possibly most other Linux [[command shell]]s (investigation needed).		This is because grep does not do its own file-filtering but relies entirely on the [[command line]] environment to translate file-mask specifications into a list of files, which are then each passed to grep as a separate argument. [[bash/globbing\|This is a feature/defect of <code>bash</code>]] and possibly most other Linux [[command shell]]s (investigation needed).

Woozle: TC post

2020-02-05T18:45:03Z

TC post

← Older revision		Revision as of 18:45, 5 February 2020
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	* will apply only to the current folder		* will apply only to the current folder
	* will prevent grep from recursively searching any folders whose names do not also match		* will prevent grep from recursively searching any folders whose names do not also match
			==Links==
			* '''2020-02-04''' [https://toot.cat/@woozle/103602468124365262 #softwareGripe #grep #counterintuitive]

Woozle: Created page with "This is because grep does not do its own file-filtering but relies entirely on the command line environment to translate file-mask specifications into a list of files, whi..."

2020-02-05T14:56:44Z

Created page with "This is because grep does not do its own file-filtering but relies entirely on the command line environment to translate file-mask specifications into a list of files, whi..."

New page

This is because grep does not do its own file-filtering but relies entirely on the [[command line]] environment to translate file-mask specifications into a list of files, which are then each passed to grep as a separate argument. [[bash/globbing|This is a feature/defect of <code>bash</code>]] and possibly most other Linux [[command shell]]s (investigation needed).

In short, grep does not have the ability to search recursively using a file-mask, and any mask entered:
* will apply only to the current folder
* will prevent grep from recursively searching any folders whose names do not also match